Fiber-faced articles, such as flooring carpets and mats, are in common use in homes, businesses and transportation vehicles such as automobiles, buses, trains, aircraft and marine craft. Such articles provide a pleasing appearance as well as comfort, warmth, and improved acoustic characteristics. It is quite common, however, for certain areas of carpet, as installed, to receive substantially more foot traffic, and thus, wear and tear, as compared with other areas. For instance, in automobiles there is frequently a greater degree of wear in the foot well of the driver's position as compared with other areas within the passenger compartment.
In order to accommodate such uneven wear in automobile carpeting, fiber-faced articles known as "throw-in mats" are frequently used to protect the high traffic areas from wear. A common problem in the use of such throw-in mats is the tendency of the floor mat to slip on the permanent carpet when such mats are constructed with a relatively smooth backing. To overcome this problem, such mats have been developed with a backing having a plurality of downward extending projections, known as nibs, which extend into and become anchored in the underlying carpet, thereby minimizing undesired lateral movement. Because the effectiveness of the nibs requires an underlying surface into which the nibs can become anchored, it is not desirable to have nibs located on those portions of a floor mat which will be placed above a hard surface such as, for example, the non-carpeted surface often found under the pedals in the driver's side floor well of an automobile. In order to overcome this problem, it is highly desirable that the process used to form such mats is capable of efficiently and economically tailoring the pattern of nibs on the floor mat to the large number of different foot well configurations found in the numerous automobiles now produced in the United States and throughout the world.
The downward projecting nibs are often formed from the main body of the backing material of the floor mat. It has been heretofore known to form mats with nibbed backings by continuous extrusion of thermoplastic material into the nip between two cooled rolls, wherein one of the rolls has small cavities therein for forming the nibs. In order to ensure the economic production of mats in this fashion, it is generally recognized that the economies of scale must be utilized, which means that such a process requires very large and expensive extrusion equipment and rolls. However, such a process is encumbered by poor flexibility in the formation of nib pattern and can not be readily adapted to the formation of mats with unusual shapes or to the formation of mats with a wide variety of nib patterns. Thus, such a process suffers from the severe disadvantage of not being practical for the formation of original equipment thrown-in mats.
A mat forming process which exhibits superior design flexibility involves the joining of preformed blanks of thermoplastic sheeting to corresponding blanks of preformed carpet. In such a process, which is generally batchwise or semi-continuous, each backing blank is joined to the carpet blank in a mold press operation of the type disclosed, for example, in U.S. Pat. No. 4,174,991--Reuben, which is incorporated herein by reference. In methods of this type, the backing/carpet combination is placed into a mold having nib cavities arranged in the desired pattern. The mold plate is typically placed on the lower platen of the press, which is heated to a relatively high temperature. The backing/carpet combination is exposed in the press to time, temperature and pressure conditions which cause the backing material to flow into and fill the nib-shaped cavities, thereby forming the nibbed portion of the mat.
In order to ensure that the backing material completely fills the cavities and thereby fully forms the desired nib, it is necessary to provide means for the air occupying the indentations to escape. This is commonly accomplished by the use of air vent channels leading out from the cavities to the edge of the mold plate. In this way, the air which occupies the nib-forming cavities in the mold plate is allowed to evacuate the cavities as the heated backing material flows in.
Applicants have recognized a problem with the use of such air vent channels in connection with previously developed methods of nib formation. More particularly, applicants have noted the tendency of such air vent channels to become blocked as the heated backing material flows not only into the cavity but also into the air vent channels themselves. Upon cooling, the material which has flowed into the air vent channels hardens and, when the floor mat is removed from the mold plate, certain nibs will bear undesirable extensions representing the additional material which has flowed into the air vent channels. Furthermore, and equally undesirable, many of the air vent channels become blocked by backing material which has cooled and remains in the channel upon removal of the mat. The resulting blockage defeats the function of the air vent channel, and additional time and labor are required to remove the backing material causing such blockage.
In view of the problems associated with the prior art, it is an object of the present invention to provide efficient and flexible methods of forming floor mats having a non-flat backing surfaces.
It is another object of the present invention to provide methods of forming floor mats comprising a fabric layer and a thermoplastic backing layer wherein the backing layer bears a plurality of integral projections.